Hayabusa2 mission: Ryugu asteroid sample continues to shed light on Earth's early evolution

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Japan's asteroid mission Hayabusa2 returned a piece of the asteroid Ryugu to Earth almost two years ago now, and that sample is still revealing valuable insights into the history of the early solar system.

A study by a group of scientists from the Institut de Physique du Globe de Paris, Université Paris Cité and CNRS1 has just revealed the isotopic composition of zinc and copper of asteroid Ryugu, a press statement reveals.

The new findings shed new light on the chemical composition of the asteroid Ryugu, which was targeted precisely because it can reveal a great deal about the early Solar System.

An ancient asteroid analysis

The isotopic signatures reveal that "Ryugu's composition is similar to Ivuna-like carbonaceous chondrites and that Ryugu-like material from the outer solar system accounts for ~5-6% of Earth's mass," the press release explains.

The scientists, who published their findings in the journal Nature Astronomy, analyzed the 5 grams of Ryugu asteroid material brought back to Earth by the Japanese space agency's (JAXA's) Hayabusa2 mission.

The first analysis of the sample was carried out by an international team, including researchers from the Institut de physique du globe de Paris, Université Paris Cité, and the CNRS. That analysis showed that the composition of the asteroid Ryugu is close to that of Ivuna-like carbonaceous chondrites (CI), which are believed to be the most chemically primitive meteorites, as they most closely resemble the composition of the Sun when compared with other asteroid types.

In their study, the international team of scientists showed that the isotopic ratios of copper and zinc in the samples from Ryugu "were identical to CI chondrites but different from all other types of meteorites." These, the press release explains, "represent the best estimate of the solar composition to date for copper and zinc."

The researchers' analysis also showed that Ryugu-like material represents about 5% of the Earth's mass, providing a fascinating window into our planet's early evolution.

JAXA chose the Ryugu asteroid as a target because its high carbon content made it a strong candidate for a space rock that could reveal a vast amount of information about the origin of life in our solar system. Previous analysis of Ryugu shows that it was originally part of a parent asteroid formed in the outer solar nebula and that much of Earth's water during its early evolution may have come from asteroids of similar composition.

The Hayabusa2 mission shed new light on Earth evolution

JAXA launched Hayabusa 2 in December 2014. The space agency's spacecraft arrived at the asteroid Ryugu in June 2018, deploying two rovers and a small lander to the space rock's surface. In February 2019, Hayabusa2 fired an impactor on the asteroid's surface to create an artificial crater from which it could retrieve rock samples.

The Hayabusa2 spacecraft then made its way home and returned a capsule containing its Ryugu asteroid samples to Earth in December 2020, after a six-year journey to the space rock and back. In a dramatic sequence of events, the spacecraft released its capsule into Earth's atmosphere for a parachute-assisted landing over rural Australia before continuing on its journey to another asteroid. JAXA will continue to search for more asteroid samples that can help the global scientific community to learn more about our solar system and the way its early composition affected the way life ultimately flourished on Earth.